Previous research (Hakes, Evans & Tunmer, 1976) has demonstrated that major changes occur in children's linguistic intuitions about synonymy, acceptability and the segmental properties of words during middle childhood (i.e., 4 through 8 years). Further, Hakes et al demonstrated that the emergence of these intuitions reflects a single underlying developmental change, one that is closely related to the development of concrete operational thinking. The proposed research will examine the emergence of these and other, related linguistic intuitions in a longitudinal study designed to provide further information about the nature of the abilities underlying such intuitions and about how their emergence is related to other aspects of cognitive development. The research will also examine the possibility that the kinds of linguistic and cognitive abilities that first emerge during middle childhood are related to the development of cerebral lateralization of linguistic functions.